Flotation screen



Oct. 15, 1929. H, B, HOUSTON 1,731,779

FLoTAToN SCREEN FiledvApIl 9, 41926 www www@ t 5mm/@mam UNITED STATESdPA'IENT orrlcl;d

FLOTATION SCREEN Application led April 9, 1926. ySerial No. 100,816.

This invention relates to screens for flotation processes and the likeand its objects are the provision of a generally improved and simpliiedscreen construction'that may be economically produced and 'which willoperate eiiiciently and positively without flexing the screen as a wholeand without requiring interconnecting grooves between the apertures oropenings through the screen.

The invention is illustrated in the accomn panying drawing in which,

- Figure 1 is a more or less diagrammatic vertical section through anillustrative flotation cell or box showing an embodiment of the presentinvention in connection therewith; y Fig. 2 is afragmentary sectionthrough the screen shown in Figure 1 and on an enlargedscale; and

Figs. 3, 4, 5, 6 and 7 are fragmentary sections similar to Figure 2 andshowing a number of different embodiments of the present i'nvention.

Referring to the drawing theiotation box or cell shown is of the typeshown in my copending application Serial No. 38,608, filed June 22,1925. This showing is merely il-` lustrative and it is to be understoodthat the screen of my present invention has utility in a wide variety offlotation machines and analogous apparatus and that therefore thedetails of a cell or box, per se, are immaterial and may be varied `asdesired.

The cell shown comprises a generally rectangular box 5 having a baffle6. The pulp may be fed into the box 5 at the left of the baiiie 6, aswell understood in the art, and the froth overflows the sides while thetailings may be discharged or withdrawn through a suitable pipe oroutlet, not shown.

The screen of Figures 14 and 2 is designated generally at 10 and in theparticular embodiment of the invention shown in Figure 1 it constitutesthe sloping-bottom of the flotation box or tank 5. Air under the desiredpressure and from a suitable source, notshown, is disseminated intofthev flotationpulp 12y through the screen 10, the air,- being broughtto the screen 10 by means of suitable conduit `:means '15. Theparticular conduit' means 15 shown has a` plurality of 'flared outlets16 for distributing the air beneath the under or inlet side of thescreen.

The screen 10 maybe mounted in any suitable or preferred manner. In theparticular embodiment shown it is mounted obliquely upon internal ledges20 to give the sloping bottom effect. The ledges 20 may be scarfed, forexample, with the screen 10 set down into the general plane of theledges and secured as by means of overlying strips 21 secured in placeby suitable fastening means 22.

The screen of Figures 1 and 2 comprises a sheet or layer 30 of resilientmaterial mounted upon a rigid backing member 32. The backing member 32may be formed of hard l rubber, metal or any other suitable or preferredmaterial and the resilient sheet or' layer 30 is preferably vulcanized,cemented or otherwise secured to the backing member 32 at 35 over itsentire area. Extending through both the backing member .32 and t-heresilient layer or sheet 30 are a mult-iplicity of apertures 36 and theair stream coming from below or from the inlet side of the .screen isVdisseminated through these apertures 36 and passes up through theoutlet side ofthe screen and into the emulsion above in a great numberof small streams or bubbles. v

In the'embodiment of Figures 1 and 2, the apertures or openings 36 areof generally conical formation, decreasing from the bottom or inlet sideof the backing member 3.2 of the screen tothe reduced or restrictedoutlets 38 opening through the upper'surface or outlet side of theresilient sheet or layer 30. The restricted outlets 38 may open directlyfrom the upper surface of the lresilient layer 30 and the enlargedinlets 40 may open di- 90 rectly from the bot-tom surface of the backingmember 32 and'there needl be no interconnectedgrooves between theapertures 36 on either side of the screen. i

The apertures 36 are shown in vFigures 1 95 andi 2 as extendingvobliquely through the screen, at least, vthey areY in Figures 1 and 2.obliquely disposed with respect to thejupper or outlet side of thelayer 30,'y so`that the Weight the water' and Ore Pulp or other 10material upon the screen 10 and particularly upon the upper surface ofthe resilient layer 3() will close the apert-ures 36 when there is no'air passing therethrough and the closing of the apertures 36 in thismanner prevents back leakage of the water or pulp and prevents the wateror pulp in detrimental quantities from passing down through the screento the inlet side.

The resilient upper sheet or layer thereby forms in effect a check valvefor closing the apertures 36 against leakage of the pulp or watertherethrough. The resilient layer 30 is preferably of relatively softrubber although any other material having the desired action may beemployed. W'hen the air is turned on the pressure thereof overcomes theaperture closing pressure imposed upon the upper surface of the screenvby the water and ore pulp thereon and the air is permittedl to passfreely through the aperture 36 and is disseminated by the screen andissues as bubbles or line streams into the overlying pulp.

In operation, the backing member 32 holds the active area of the layeror sheet- 30 substantially rigid or in substantially fixed position. Theapertures 36 may be normally open, i.l e., in the absence of thepressure im posed upon the upper surface of the screen by the weight ofthe water and pulp thereon or at least said a ertures 36 are openedwithout flexing the s eet or layer 30 asa whole and without lifting itfrom the backing member 32 by the pressure of the air on the with thebacking member holding said layer 30 rigid or in fixed position as wholeand against bodily downward iexing causes an internal compression of thelayer 30 and it is this'nternal compression and accompanying internaldisplacement of the material of the sheet 30 that closes the apertures36 and im` parts the selfesealing act-ion against downward flow orleakage of the pulp or water through the screen.

In the form of screen of Figures l and 2v the oblique or diagonaldisposition 0f the apertures 36 or at least the oblique or diagonaldisposition of the upper ends of the apertures 36 withrespect to the topor upper surface ofthe soft rubber or resilient sheet 30 particularlyada ts the sheet 30 for closing the vapertures 36 y the Weightof theoverlying thereof and these overlying portions are y forced orcompressed down by the overlying material and close the apertures 36when air is not being passed through the screen. The internalcompression of the sheet or layer 30 may also set up a lateraldisplacement of the material in the sheet which may further aid inclosing and sealing the apertures through the sheet. The enlarged inlet40 facilitates the entry of the air or other fluid under pressure intothe apertures from the inlet side of the screen When the air is turnedon or a flow of air is set up through the screen.

In the embodiment of Fig. 3, the relatively soft resilient material orsoft rubber upper layer of the screen is designated at 42 and the rigidbacking is designated at 43. In this case, the apertures through thescreen comprise straight or non-conical portions 45 through therelatively soft resilient upper layer and conical portions 46 openindownwardly through the lower layer or acking 43 therefrom and of conicalformation providing enlarged inlets 48 at the bottom surface of thebacking 43. This gives the upper restricted outlets 45 a somewhatgreater length for the self-closing action by the Weights of theoverlying material Without sacrificing the enlarged inlets 48 at thebottom surface of the backing 43. The apertures of Fig. 3 are as in theprevious embodiment shown as disposed obliquely through the screen. y

In the embodiment of Fig. 4, the apertures 50 are of generally conicalformation with the enlarged inlets at the bottom and t-he restrictedoutlets at the top. In this ease, however, the apertures 50 are shown asextending vertically or perpendieularly through the screen 52. In thisease, the conical formation of the apertures 50 provides some overhangof the upper layer so that upon compression thereof by the overlyingweight along with the lateral internal displacement of the materialofthe upperl layer which accompanies the compression thereof positivelyand effectively closes the apertures 50 when air is not being passedthrough the screen.

In the embodiment of Fig. 57 the apertures 53 are shown in the form ofstraight holes extending vertically or perpendicularly through thescreen 54. lIn this case, there is no appreciable overhang of thematerial of the upper soft layer and the closing of the apertures 53 isby the internal lateral displacement of the material of the upper'softlayer 55 which is set up by the compression imposed uponthe layer 55 bythe overlying material. p

In the embodiment of Fig. 6, thev apertures 58 are in the form ofstraight openings extending obliquely through the upper layer 59 andlower backing member 60 of the screen. In this case the overhang isagain present and the openings are sealed by the `compression andaccompanying internal displacement of the material of the upper layer 59which is caused by the weight of the overlying material when air is notbeing passed through the screen.

. panying compression of thesheet 63 closes the apertures 62.

I do not intend to be limitedto the precise details of construction norto the particular l' use or application shown or described.-

tion and against bodily flexing in rection.

1. A flotation screen comprising a layer of resilient material providedwith apertures therethrough and mearfs holding the active area of saidlayer in substantially fixed posieither di- 2. A flotation screencomprising a layer of resilient material, said resilient layer having aplurality of apertures extending therethrough, said apertures beingclosed by internal displacement of the resilient material and meansholding the active area of said layer in substantially fixed positionand against bodily flexing in either direction.

3. A flotation screen comprising a layer of resilient material having aplurality of apertures therethrough, said resilient layer beingrelatively thick and soft to permit opening and closing of saidapertures by internal displacement Within the body of theresilient layerand without stretching or bodily7 flexing the resilient layer and meansholding said layer against bodily7 flexing in either direction.

4. A flotation screen comprising a layer of resilient material having aplurality of normally open apertures therethrough and means holding saidlayer against bodily flexf ing in either direction.

5. A flotation screen comprising a layer of rubber having a plurality ofapertures therethrough, said layer being of a thickness and softnesspermitting closing of said aperturesjby internal displacement of therubber and without'flexing the layer as a whole and means for holdingsaid layer against bodily flexing.

6. A flotation screen comprising a layer of relatively soft resilientmaterial, said layer having a plurality of apertures therethrough andsaid apertures 'being closed by internal compressionl of the 'resilientmaterial from its normal condition and means holding said layer againstbodily flexingin either direction.

7. A flotation screen comprising a rigid backing and a layer ofrelatively sofiJ resilient material attached to said backing throughoutthe entire active area of the screen for pre venting bodily flexingthereof, said screen having a plurality of apertures extending throughsaid backing and through said relatively soft resilient layer.

8. A flotation screen comprising a rigid backing having aperturestherethrough and a layer of soft rubber attached to said backignthroughout the entire active area of the screen for preventing bodilyflexing thereof, and having apertures registering with the apertures insaid backing. Y

9. A flotation screen comprising a hardy rubber backing and a layer ofsoft rubber vulcanized to said backing over the active area of thescreen, said screen having apertures 'extending through said soft rubberlayer and through said backing. l

10. In flotation apparatus the combination of a chamber adapted tocontain flotation pulp having a wall of resilient material provided withopenings therethru, means for admitting fluid under pressure to theouter side of the resilient wall, said wall being relatively thick andsoft with the openings therethru open in the normal condition of thewall, means for holding said wall against bodily flexing, said-openingsbeing capable of being closed by internal displacement produced in theresilient wall by the force of the pulp on one side and being capable ofbeing opened by overcoming, by the pressure of the fluid admitted to thev,opposite side, the internal displacement produced by the pulp.

In witness whereof, I hereunto subscribe my name this 27 day of March,1926.

v HENRY B. HOUSTON.

